1. Field of the Invention
The present invention relates to an optical installation for determining the relative positions of at least two objects in space. The optical installation comprises at least two optical systems each associated with an observation frame, the optical systems each being adapted for the determination of the position of an object in space with respect to its observation frame, on the basis of an image of the object which is captured by the optical system.
It furthermore relates to a process for determining the relative positions of at least two objects in space. The process implements at least two optical systems each associated with an observation frame, the optical systems each being adapted for the determination of the position of an object in space with respect to its observation frame, on the basis of an image of the object which is captured by the optical system.
2 Description of the Related Art
For checking the geometry of an automotive vehicle, it is necessary to ascertain the relative positions of the wheels of the vehicle. This information makes it possible to check and optionally correct the parallelism of the wheels and in particular the geometry of the vehicle.
To this end, various installations and processes are known which it make possible, with the aid of several optical systems each observing a wheel of the vehicle, to determine the relative positions of these wheels. Such devices and processes are described for example in the documents WO-94/05969 and U.S. Pat. No. 5,675,515.
In these installations, the optical systems are formed by independent cameras, or a single camera associated with sets of lenses defining separate optical paths for one and the same incident beam. The optical systems allow simultaneous observation of the wheels of the vehicle and, on the basis of the images of the wheels, make it possible to determine their relative positions.
To this end, it is necessary for the various optical systems, to be in known relative positions, otherwise it is impossible to correlate the information obtained from the images of each wheel. To guarantee fixed relative positions of the optical systems with respect to one another, the devices described in these documents provide for rigid mechanical structures on which the optical systems are immobilized.
The presence of rigid mechanical structures of this kind renders the installation bulky. Moreover, the latter is fragile since the deformation, for example following unintentional knock, of the rigid mechanical structures leads to errors in measuring the relative positions of the wheels of the vehicle.
The object of the invention is to propose an optical installation and process for determining the relative positions, in space, of at least two objects, especially wheels of vehicles, the installation having reduced bulk, being easy to implement and having reduced sensitivity to the harsh conditions encountered in a garage.
To this end, the subject of the invention is an optical installation for determining the relative positions of at least two objects in space, of the aforesaid type, characterized in that the optical systems are movable with respect to one another, in that an optical system, constituting an optical reference system, comprises a set of reference points, of known geometrical configuration. The set of reference points is immobilized in a known position with respect to the observation frame of the optical reference system, and is visible from each optical system in the absence of objects, in that each optical system comprises means for analyzing an image of the set of reference points and means for positioning the set of reference points with respect to its observation frame, and in that it comprises means for deducing the position of the observation frame of each optical system with respect to the observation frame of the optical reference system, on the basis of the position of the set of reference points with respect to each observation frame, and of known position of the set of reference points with respect to the observation frame of the optical reference system.
According to particular embodiments, the optical installation comprises one or more of the following characteristics.
Each optical reference system comprises a video camera supported by a leg and connected to a same central information processing unit. The set of reference points comprises a group of coplanar discrete visible marks as well as at least one non-coplanar visible mark. The installation comprises pads, each adapted so as to be secured to an object in a known position, and in that each optical system comprises means for determining the position of a pad in space with respect to its observation frame and means for deducing the position of the object with respect to its observation frame from the determined position of the pad with respect to its observation frame and from the known position of the pad with respect to the object.
The installation comprises four optical systems which are intended to be disposed substantially at the vertices of a quadrilateral for the determination of the relative positions of four objects in space, the objects being disposed inside the zone delimited by the quadrilateral. The installation can comprise two optical installations as defined above, the set of reference points of a first optical reference system being visible from the second optical reference system in the absence of objects. The second optical reference system comprises means for analyzing an image of the set of reference points of the first optical reference system and means for positioning the set of reference points with respect to its observation frame. It also comprises means for deducing the position of the observation frame of the second optical reference system with respect of the observation frame of the first optical reference system, on the basis of the position of the set of reference points of the first optical reference system with respect to the observation frame of the second optical reference system, and of the known position of the set of reference points of the first optical reference system with respect to the observation frame of the first optical reference system. It further comprises means for deducing the relative positions of the observation frames of each optical system.
The subject of the invention is moreover an optical process for determining the relative positions of at least two objects in space, of the aforesaid type, characterized in that the optical systems are movable with respect to one another, in that the optical system, constituting an optical reference system is furnished with a set of reference points, of known geometrical configuration. The set of reference points is immobilized in a known position with respect to the observation frame of the optical reference system, and is visible from each optical system in the absence of objects, in that each optical system analyzes an image of the set of reference points and determines positioning of the set of reference points with respect to its observation frame. The position of the observation frame of each optical system with respect to the observation frame of the optical reference system is deduced on the basis of the positioning of the set of reference points with respect to the observation frame, and the known position of the set of reference points with respect to the observation frame of the optical reference system.